/etc/mtab symlink to /proc/self/mounts

Hi
I use el6 based Live CDs and I think this last commit is causing the 
liveinst  anaconda scripts some headaches.  After pulling version 16.3 
of the tools from the git repo and updating my Build Host, I started 
having problems doing  install to HD from LiveCD.

Basically, anaconda included in el6 and el6u1 assumes that /etc/mtab is 
a regular file with rw attributes.
When the installer tries to open the file for writing and populate it,  
we are getting a traceback  because /etc/mtab is symlinked to 
/proc/self/mounts  and that file is not writable.

If it is necessary to symlink /etc/mtab to proc/self/mounts in the 
livecd creator tool, would it be possible to implement a fix for 
anaconda scripts that do not like seeing /etc/mtab as a link to a read 
only /proc file?

**Commit:
http://git.fedorahosted.org/git/?p=livecd;a=commit;h=9e431a9c86398705ec7b303...

diff --git a/imgcreate/creator.py 
http://git.fedorahosted.org/git?p=livecd;a=blob;f=imgcreate/creator.py;h=ec4c1ba82fb00a3360362a26ab8fd0be8c1a58ae;hb=731ba56081dcc580b314d3214d0758a932a96118 
b/imgcreate/creator.py 
http://git.fedorahosted.org/git?p=livecd;a=blob;f=imgcreate/creator.py;h=675dcf6cdf3e34b03ae3dd0ada5498b1faefa32b;hb=9e431a9c86398705ec7b30328dc0981539e15a40
index ec4c1ba 
http://git.fedorahosted.org/git?p=livecd;a=blob;f=imgcreate/creator.py;h=ec4c1ba82fb00a3360362a26ab8fd0be8c1a58ae;hb=731ba56081dcc580b314d3214d0758a932a96118..675dcf6 
http://git.fedorahosted.org/git?p=livecd;a=blob;f=imgcreate/creator.py;h=675dcf6cdf3e34b03ae3dd0ada5498b1faefa32b;hb=9e431a9c86398705ec7b30328dc0981539e15a40 
100644(file)
--- a/imgcreate/creator.py 
http://git.fedorahosted.org/git?p=livecd;a=blob;f=imgcreate/creator.py;h=ec4c1ba82fb00a3360362a26ab8fd0be8c1a58ae;hb=731ba56081dcc580b314d3214d0758a932a96118
+++ b/imgcreate/creator.py 
http://git.fedorahosted.org/git?p=livecd;a=blob;f=imgcreate/creator.py;h=675dcf6cdf3e34b03ae3dd0ada5498b1faefa32b;hb=9e431a9c86398705ec7b30328dc0981539e15a40
@@ -536,7 
http://git.fedorahosted.org/git?p=livecd;a=blob;f=imgcreate/creator.py;h=ec4c1ba82fb00a3360362a26ab8fd0be8c1a58ae;hb=731ba56081dcc580b314d3214d0758a932a96118#l536 
+536,7 
http://git.fedorahosted.org/git?p=livecd;a=blob;f=imgcreate/creator.py;h=675dcf6cdf3e34b03ae3dd0ada5498b1faefa32b;hb=9e431a9c86398705ec7b30328dc0981539e15a40#l536 
@@ class ImageCreator(object):
          self.__create_minimal_dev()
-        os.symlink("../proc/mounts", self._instroot + "/etc/mtab")
+        os.symlink("/proc/self/mounts", self._instroot + "/etc/mtab")
          self.__write_fstab()
@@ -548,11 
http://git.fedorahosted.org/git?p=livecd;a=blob;f=imgcreate/creator.py;h=ec4c1ba82fb00a3360362a26ab8fd0be8c1a58ae;hb=731ba56081dcc580b314d3214d0758a932a96118#l548 
+548,6 
http://git.fedorahosted.org/git?p=livecd;a=blob;f=imgcreate/creator.py;h=675dcf6cdf3e34b03ae3dd0ada5498b1faefa32b;hb=9e431a9c86398705ec7b30328dc0981539e15a40#l548 
@@ class ImageCreator(object):
          from the install root.
          """
-        try:
-            os.unlink(self._instroot + "/etc/mtab")
-        except OSError:
-            pass
-
          self.__destroy_selinuxfs()
          self._undo_bindmounts()

**Install to HD Failure:
The failure looks like

Traceback (most recent call first):
    File "/usr/lib/anaconda/livecd.py", line 408, in doPostInstall
    f.close()
    File "/usr/lib/anaconda/backend.py", line 239, in doPostInstall
    anaconda.backend.doPostInstall(anaconda)
    File "/usr/lib/anaconda/dispatch.py", line 208, in moveStep
    rc = stepFunc(self.anaconda)
    File "/usr/lib/anaconda/dispatch.py", line 126, in gotoNext
    self.moveStep()
    File "/usr/lib/anaconda/gui.py", line 1381, in nextClicked
    self.anaconda.dispatch.gotoNext()
    File "/usr/lib/anaconda/iw/progress_gui.py", line 79, in renderCallback
    self.intf.icw.nextClicked()
    File "/usr/lib/anaconda/gui.py", line 1402, in handleRenderCallback
    self.currentWindow.renderCallback()
    IOError: [Errno 22] Invalid argument
    ...
    IOError: [Errno 22] Invalid argument

Local variables in innermost frame:

**Simple test:
When I echo foo into /proc/self/mounts ..
[root@bur374-199 ~]# echo foo >> /proc/self/mounts

-bash: echo: write error: Invalid argument

...Looks like the anaconda python exception.

**Workaround:
I think this file from anaconda package /usr/lib/anaconda/livecd.py , 
needs to take into account the possibility that /etc/mtab is symlinked 
to a ro file in proc and either do nothing  (patch below),  or unlink 
and create a regular file before trying to write data.

I have had to add this patch to my el6 finish scripts as a workaround.
###Finish script to fix anaconda liveinst  when /etc/mtab is symlinked
%post

cat > /tmp/apatch << EOF_patch
--- /usr/lib/anaconda/livecd.py 2011-06-10 12:53:52.141225479 -0400
+++ /usr/lib/anaconda/livecd.py_new     2011-06-10 12:57:17.190133970 -0400
@@ -403,9 +403,10 @@

# now write out the "real" fstab and mtab
          anaconda.id.storage.write(anaconda.rootPath)
-        f = open(anaconda.rootPath + "/etc/mtab", "w+")
-        f.write(anaconda.id.storage.mtab)
-        f.close()
+       if not os.path.islink("/etc/mtab"):
+            f = open(anaconda.rootPath + "/etc/mtab", "w+")
+            f.write(anaconda.id.storage.mtab)
+            f.close()

# copy over the modprobe.conf
          if os.path.exists("/etc/modprobe.conf"):
EOF_patch
patch -d /usr/lib/anaconda < /tmp/apatch

Thanks
Gregory Fowler

[Brian C. Lane]

On Mon, Jun 20, 2011 at 04:56:59PM -0400, Gregory Fowler wrote:
> Hi
> I use el6 based Live CDs and I think this last commit is causing the
> liveinst  anaconda scripts some headaches.  After pulling version
> 16.3 of the tools from the git repo and updating my Build Host, I
> started having problems doing  install to HD from LiveCD.

To build el6 live images you should be using the version from EPEL6, not
the one from rawhide. Or the one from F13, which is exactly the same as
the EPEL6 version right now.